The exchanges between the mayor and Boro Taxi boss Mohammed Bashir include Mr Mallon’s take on more of his council colleagues.

Last week it was revealed that Mr Mallon had used an inappropriate sexual analogy to refer to a council official during the secretly recorded conversations.

And the second installment of tapes, revealed exclusively by the Evening Gazette’s sister paper The Sunday Sun, include Mallon calling one Labour councillor “******* biased” about the ongoing feud over the taxi trade in the town. He also promises Mr Bashir, who was involved in a lengthy legal battle with the council: “By the time I’m finished I’m gonna have this ******* Labour group swear with you as well.”

In other tapes, the mayor talks of his fury at another Labour councillor, Barry Coppinger, who wrote to a supermarket appearing to back Boro Taxis’ competitors.

Mallon said: “You can sense my ******* venom.” He added: “I could wring his neck, what I think of him.”

Last night, Cllr Coppinger said: “I think that’s all in the past. The letter that I sent to Morrisons was trying to resolve things in a positive way.”

The mayor is also under fire from Asian taxi-drivers on Teesside after he appeared to target them as “badly behaved” last week.

Hackney carriage driver Rasub Afzal has written a letter to Town Hall bosses speaking for “several” other Asian taxi drivers.

It reads: “I wish it to be known that his reference to Asian taxi drivers is unacceptable, is encouraging to those who are racist and remains unexplained.”

The mayor said he was referring specifically to a group who were overcharging customers and claimed people had come out to publicly support him on the issue. The revelation of the secret tapes are the latest development in the feud between Middlesbrough Council and Boro Cars. Last week Mr Mallon claimed Mr Bashir had become obsessed with the conflict between Hackney cabs, private hire cabs and Middlesbrough Council.

Yesterday Mr Mallon said he was saddened that Mr Bashir had behaved as he has.

He added: “It seems he has been secretly taping our private conversations from the time I wrote to him and made clear that, although we were friends, it would not impact on my decision making. His reaction has been to release covertly recorded tapes of private conversations to the Sunday Sun in a bid to prevent me being re-elected as Mayor - clearly he thinks he will have a better chance of getting his way under a new mayor.”

He adds: “One thing is clear to all, if I had given Mr Bashir what he wanted he would not have released these tapes so that shows my decision making was not improper in any way.”

Mr Mallon added today: “The people of Middlesbrough know my style and they will let me know on Thursday if they want me to carry on. The most important thing is that people get out and vote regardless of who they vote for.”